JP2007120302A - Soil improvement method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make soil improvements so as to acquire high hardness and strength, without requiring the addition of a large amount of hydraulic hardening agent or earth removal, in the case of surface-layer and column-shaped soil improvement work on weak subsoil such as soil of the loamy layer of the Kanto district or humus soil. <P>SOLUTION: The ground is excavated without requiring the removal of earth in the improvement of soil, containing a large amount of soil of the loam layer of the Kanto district or humus soil. Earth, sand, and cement are added to excavated soil. The excavated soil is mixed with added earth, sand, and cement and agitated to harden the excavated soil and mixed and agitated as adding water if required. Since earth and sand are added in addition to cement, it is possible to improve soil of sufficient hardness and strength with the addition of a relatively small amount of cement without requiring earth removal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention excavates the ground without draining, and mixes and stirs the excavated excavated soil and a hydraulic hardening agent (cement-based or lime-based powder or slurry (milk or mud)) such as cement. The present invention relates to a ground improvement method for hardening (solidifying or solidifying) the ground.

  As a foundation of construction, ground improvement of soft ground is widely performed. The ground improvement includes a surface layer (planar or flat plate) improvement that improves the ground in a relatively shallow area and a columnar improvement that improves the ground relatively deeply. In the surface layer improvement, for example, excavation is performed on the backhoe without draining the ground, and the excavated soil and a hydraulic hardener such as cement are mixed and stirred to improve the ground in a predetermined area.

  In addition, the columnar improvement is performed by, for example, using a ground improvement device having a drilling blade at the lower end of the drilling shaft and a stirring blade on the bottom, rotating the drilling shaft to form a soft ground with the drilling blade or the stirring blade. Then, excavating without discharging, into the excavated soil, discharge an aqueous slurry containing a hydraulic hardening agent from the tip of the excavation shaft (hereinafter also simply referred to as slurry), mix this slurry and excavated soil, Stir to improve the ground into a columnar shape.

  However, even with such ground improvement, the soil ground (mainly composed of volcanic ash and pumice), represented by the Kanto Loam Formation, does not increase the hardness (consolidation) hardness of the ground, and the strength There was a problem that it was not. This is because the Kanto Loam soil is rich in volcanic ash. Moreover, even in the ground having a soil layer containing a lot of accumulated humic substances such as humus soil, there is a problem that the ground does not increase in hardness and strength. This is because humus soil is derived from its components, has a high moisture content, and has a dense soil quality.

  For this reason, in the improvement of the soft ground in such soil (soil, geology), it was necessary to add more hydraulic hardener than necessary. On the other hand, it was pointed out that despite the addition of many hydraulic hardeners, it was impossible to improve the hardness and strength of the ground, and there was a problem as a building foundation. . In addition, such ground improvement requires a lot of hydraulic curing agent, leading to an increase in construction cost. Furthermore, if a large amount of hydraulic hardener is used, the elution of contaminants such as hexavalent chromium contained in cement and the like into the soil also increases, which causes environmental problems. For this reason, in improving the surface ground of humus soil, the humus soil to be improved is excavated and discharged, and another high-quality earth and sand is added to it, and then a hydraulic hardening agent is added and mixed. In some cases, in this case, the construction cost was significantly increased by the amount of earth required.

  The present invention has been made to solve the above problems, and in soft ground such as Kanto loam soil or humus soil, in the case of surface layer or columnar ground improvement work, a large amount of hydraulic hardening agent is added. It is another object of the present invention to provide a ground improvement method having high hardness and strength without requiring soil removal.

  The ground improvement method according to claim 1 for achieving the above object is the method of excavating the ground without draining, adding earth and sand and a hydraulic hardening agent to the excavated soil, and adding the excavated soil. It is a ground improvement method characterized by hardening the ground excavated by mixing and stirring earth and sand and a hydraulic hardening agent.

  In this way, at the site of ground improvement, not only hydraulic hardeners but also earth and sand were added to the excavated soil and mixed and stirred, so a large amount of soil and humus soil containing a large amount of Kanto Loam soil was added. Even in the soil improvement of the soil contained in the soil, it is possible to obtain a ground having high hardness and strength without adding only a large amount of a hydraulic curing agent and without requiring soil removal. It is effective in improving the ground of soil where hardness and strength are particularly difficult, such as humus soil. In addition, the amount of hydraulic hardening agent added may be the amount generally added to the volume of ground that should be improved in normal soft ground, and is the sum of the amount of earth and sand to be added and the amount of excavated soil to be excavated. May be set as the volume of the ground to be improved. In addition, what is necessary is just to set the quantity of the earth and sand to add suitably according to the soil quality of construction and construction object in the range in which the hardness and intensity | strength after hardening are ensured.

  In the present invention, examples of the hydraulic curing agent include Portland cement, fly ash cement obtained by mixing fly ash and silica with Portland cement, blast furnace cement, and cement (mixed cement) such as silica cement. it can. Further, as the earth and sand to be added, high-quality earth is preferable, but either clayey earth or sandy earth may be used. However, coarse particles, fine particles of sand, coarse particles obtained by drying clay and finely divided particles, fine particles, and particles may be used. Moreover, you may use what grind | pulverizes and grinds gravel and crushed stone finely.

  The ground improvement method according to claim 2 excavates the ground without draining, and simultaneously adds earth and sand and hydraulic hardener to the excavated soil, and the excavated soil and the added earth and sand and hydraulic hardener. A ground improvement method characterized in that the ground excavated by mixing and stirring is hardened. The earth and sand and the hydraulic curing agent may be added separately. However, if they are added simultaneously as in the present invention, the construction becomes easier and the construction time is shortened. In addition, it is good to prepare beforehand the thing (ground improvement material) which contains earth and sand and a hydraulic hardening agent, and mixes and stirs this earth and sand and this hydraulic hardening agent. According to such a ground improvement material, construction can be easily performed by bringing it into the ground site to be improved. The ground improvement method according to claim 3 is the ground improvement method according to claim 1, wherein an appropriate amount of water is added to the excavated soil, the added earth and sand, and the hydraulic hardening agent, and the mixture is stirred. . If the water content is high, it is not necessary to add water, but if the water content is low, an appropriate amount of water is separately added and mixed and stirred.

  The ground improvement method according to claim 4, wherein the ground is excavated without discharging, an aqueous slurry formed by mixing and stirring the earth and hydraulic hardening agent is added to the excavated soil, the excavated soil, and the addition The ground improvement method is characterized in that the ground excavated by mixing and stirring with the aqueous slurry is hardened.

  In Claims 1-3, the hydraulic curing agent is preferably added as a powder. However, since it becomes easy to mix more homogeneously by making it the aqueous slurry formed by mixing with earth and sand with water and adding as this aqueous slurry as described in Claim 4, preferable hardness is obtained. The columnar improvement is particularly effective because it is easy to mix and agitate with excavated soil. Moreover, since it is not necessary to separately stir and mix water, the construction can be simplified.

  The ground improvement method according to claim 5 is the ground improvement method according to any one of claims 1 to 4, wherein the earth and sand are finely divided. Moreover, the ground improvement method of Claim 6 is a ground improvement method in any one of Claims 1-5 whose said ground is the soil which contains a large amount of Kanto loam soil. And the ground improvement method of Claim 7 is a ground improvement method in any one of Claims 1-5 whose said ground is the soil which contains a large amount of humus soil. In addition, the term “large amount” in claim 6 or 7 refers to a case where the Kanto loam soil or humus soil contains 30% by weight or more based on the total weight of the soil in the field.

  As is clear from the above explanation, according to the present invention, it is necessary to add a large amount of hydraulic hardening agent or to remove soil even in surface improvement and columnar ground improvement in soil containing a lot of Kanto loam soil and humus soil. Therefore, it is possible to easily improve the ground with high hardness and strength.

  An embodiment of the method according to claim 1 of the present invention will be described. For example, in the surface improvement of the geology of Kanto loam soil or humus soil, the ground surface (region) to be improved is excavated with a backhoe without discharging. Then, cement (powder) is added to the excavated soil as high-quality earth and sand and a hydraulic hardening agent, and mixed and stirred so that they are homogeneous. At this time, the amount of earth and sand to be added is set according to the quality of excavated soil so that desired hardness and strength can be obtained when cement is added, mixed and stirred to be hardened. This is because even Kanto loam soil or humus soil varies in hardness and strength depending on the site. Further, if the water content is low, mixing and stirring are appropriately performed while sprinkling water.

The amount of cement may be set to an appropriate amount with respect to the total amount of excavated soil and added earth and sand, as in the case of normal soil quality. For example, the cement powder is 80 kg for a total of 1 m ³ of excavated soil and added soil. Further, an appropriate amount of water may be added according to the water content of the ground or geology.

  Thus, the excavated soil and the added earth and sand and cement are mixed and stirred. However, if necessary, the ground surface is pressurized. Then, the ground is improved by hardening (consolidating) the ground after being left, excavated and mixed and stirred. Thus, even in soil improvement including a large amount of Kanto Loam soil and humus soil, desired consolidation hardness can be obtained and high strength ground can be obtained.

  In the above description, the case where earth and sand and a hydraulic hardening agent (powder) are separately added to the excavated excavated soil and mixed and stirred is described, but these may be added simultaneously. In the case of simultaneous addition in this way, it is prepared in advance as a mixture (ground improvement material) of the sand and powder hydraulic hardening agent mixed and stirred at a predetermined ratio, and this is added to the excavated soil. Then, mixing and stirring may be performed. In the case of construction in this way, it becomes easy to mix earth and sand and cement into excavated soil, and the construction process can be simplified. In addition, the mixing ratio at the time of preparing as what mixed and stirred earth and sand and a hydraulic hardening | curing agent (powder) is set suitably according to the geology of an improvement field beforehand. However, it is preferable that various mixing ratios of earth and sand and cement be made easy.

  In the above-described embodiment, the case where the earth and sand and the hydraulic hardener (cement) are added to the excavated soil and mixed and stirred is described. However, an aqueous slurry formed by mixing and stirring the earth and sand and the hydraulic hardener is added to the excavated soil. The excavated soil and the added aqueous slurry may be mixed and stirred, and then the ground may be hardened. The aqueous slurry is, for example, one obtained by adding 80 liters of water to 100 kg of cement powder and stirring the mixture, and then adding earth and sand to the cement ratio of 30%. In the above description, cement (powder) is used as the hydraulic curing agent, but the present invention is not limited to this.

  In the above description, the surface layer improvement is described. However, the present invention can also be applied to the case where the ground improvement is a columnar improvement. However, in this case, it is preferable to add an aqueous slurry obtained by mixing and stirring earth and sand and a hydraulic curing agent and mixing and stirring with excavated soil. This is because when an aqueous slurry is added, it is easy to mix and agitate it with excavated soil even in deep columnar improvement.

  In order to improve the ground to a columnar shape, it is a hollow excavation shaft (rotation drive shaft), which is provided with a conventionally known excavation agitation device having an excavation blade at the tip and a stirring blade on the excavation shaft. The ground is excavated by rotating, moving downward and moving up. Then, the prepared aqueous slurry is pumped through a tube, mixed and stirred while being discharged and added to the excavated soil from the tip through the excavating shaft, and the ground is hardened in a columnar shape, for example. The column thus obtained has high hardness and strength.

  Incidentally, such a slurry can be produced as follows. For example, it is prepared by adding a proper amount of cement and finely divided earth and sand to a certain amount of water stored in a tank and mixing them.

Claims (7)

  Excavate the ground without draining, add earth and sand and hydraulic hardener to the excavated soil, and mix and agitate the excavated earth and the added earth and hydraulic hardener to harden the excavated ground. A ground improvement method characterized by that.   Excavate the ground without draining, add earth and sand and hydraulic hardener to the excavated soil at the same time, mix the excavated soil with the added earth and hydraulic hardener, stir the excavated ground The ground improvement method characterized by making it do.   The ground improvement method according to claim 1, wherein an appropriate amount of water is added to the excavated soil, the added earth and sand, and the hydraulic hardener, and the mixture is stirred.   Excavate the ground without draining, add the ground slurry and hydraulic hardener to the excavated soil, add an aqueous slurry that is agitated, mix the agitated soil with the added aqueous slurry, excavate A ground improvement method characterized by curing the ground.   The ground improvement method according to any one of claims 1 to 4, wherein the earth and sand are finely divided.   The ground improvement method according to any one of claims 1 to 5, wherein the ground is a soil containing a large amount of Kanto Loam soil.   The ground improvement method according to any one of claims 1 to 5, wherein the ground is soil containing a large amount of humus soil.